German patent publication 43 27 585 describes an air spring whose rolling-lobe flexible member is attached with a sealing bead to a conical sealing seat of an attachment part. No details are provided as to the type of attachment. Air springs of this kind are in use in a multiplicity of embodiments. The solution of the attachment of the rolling-lobe flexible member to an attachment part, which is shown in German patent publication 43 27 585, can be considered as a typical embodiment. The attachment part is essentially configured as a conical plate and has an air connection which often also functions simultaneously as an attachment element. Versions having several air connections and additional connections are possible. In addition to the connections, the conical plates comprise primarily two pieces of sheet metal welded to each other, namely, a round disc and a conical ring. The conical ring is in most instances only spot welded and not continuously welded to the round disc for simplification and to avoid warpage of the round disc. When the rolling-lobe flexible member is vulcanized to the attachment part, the vulcanization region must be coated with a bonding agent in a separate work step in advance of the vulcanization. One conical plate is then placed in the opening of the rolling-lobe flexible member blank in the manufacturing process. The opening lies opposite to the opening assigned to the rolling-lobe flexible member and the rolling-lobe flexible member is vulcanized to the conical plate in the vulcanization press.
This type of attachment has the following disadvantages:
a complex welding process is required for the air connection and the additional connections;
an unwanted gap can occur between the conically-shaped ring and the round disc when spot welding. The rubber can flow through this gap into the interior of the flexible member during the vulcanization process;
a tightness control is needed in order to check the quality of the weld seams at the connections; and, the conical plate must be protected against corrosion.
The air connections are furthermore configured as pivot parts and are therefore cost intensive.